Field of the Invention
The present invention relates to an electrophotographic photoreceptor.
Description of the Related Art
In recent years, it has become mainstream to use toner having a small particle size in an electrophotographic image forming apparatus as a demand for a high-definition and high-quality image has increased. Toner having a small particle has a great adhesivity to the surface of an electrophotographic photoreceptor (hereinafter, also referred to as the “photoreceptor”). Hence, it is required to increase the abutting pressure of the cleaning blade to the photoreceptor in order to realize high cleaning property, and as a result, the surface of the photoreceptor is worn by the repeated use of the photoreceptor in some cases.
As a means to decrease the adhesivity between the surface of the photoreceptor and the toner and to increase the cleaning property, it has been known to add a fluorine-based material such as fluorine-based fine particles or a fluorine-based lubricant to the protective layer of a photoreceptor. However, the hardness of the surface of the protective layer is likely to be insufficient when the amount of the fluorine-based material added is great.
In addition, a fluorine-based material is likely to migrate to the surface of the film of a coating material for protective layer in the coating material. For this reason, the fluorine-based material tends to be present only on the surface and in the vicinity thereof of the photoreceptor (protective layer) at a high concentration. Hence, in the case of using the photoreceptor in an image forming apparatus, high cleaning property is exhibited in the beginning but the cleaning property is insufficient in some cases when the surface of the photoreceptor is shaved in association with repeated use of the photoreceptor.
In the techniques for improving both the wear resistance and cleaning property of a photoreceptor, for example, a protective layer formed of the polymerized and cured product of a radically polymerizable composition containing a urethane acrylate having a perfluoropolyether moiety, a tri- or higher functional radically polymerizable monomer, and a radically polymerizable compound having a charge transport structure is known (for example, see JP 2012-128324 A).
In addition, in the techniques for maintaining both the toner releasing property and low wear property of the surface even after printing a great number of sheets, for example, a protective layer which contains perfluoropolyether and has a proportion of the number of fluorine atoms to the number of carbon atoms of 0.10 or more and 0.40 or less is known (for example, see JP 2015-028613 A).
In addition, in the techniques for enhancing the hardness and scratch resistance of the surface of a photoreceptor and the durability of the photoreceptor, a protective layer formed through polymerization and crosslinking of a polymerizable compound with a surface-treated metal oxide is known (for example, see JP 2012-078620 A).
However, even in the case of using the protective layers described in JP 2012-128324 A and JP 2015-028613 A, there is a case in which a decrease in properties such as wear resistance or scratch resistance due to the mechanical strength is observed when the content of the perfluoropolyether compound is high and high cleaning property is not sufficiently maintained when the photoreceptor is repeatedly used when the content of the perfluoropolyether compound is low. Hence, there is room for investigation in the photoreceptor of the related art from the viewpoint of sufficiently exerting the wear resistance, the scratch resistance, and the cleaning property.